title: An arsenate reductase homologue possessing phosphatase activity from sweet potato (Ipomoea batatas [L.] Lam): kinetic studies and characterization.
abstract: A cDNA encoding a putative arsenate reductase homologue (IbArsR) was cloned from sweet potato (Ib). The deduced protein showed a high level of sequence homology (16-66%) with ArsRs from other organisms. A 3-D homology structure was created based on AtArsR (PDB code 1T3K ) from Arabidopsis thaliana. The putative active site of protein tyrosine phosphatase (HC(X)(5)R) is conserved in all reported ArsRs. IbArsR was overexpressed and purified. The monomeric nature of the enzyme was confirmed by 15% SDS-PAGE and molecular mass determination of the native enzyme via ESI Q-TOF. The IbArsR lacks arsenate reductase activity but possesses phosphatase activity. The Michaelis constant (K(M)) value for p-nitrophenyl phosphate (pNPP) was 11.11 mM. The phosphatase activity was inhibited by 0.5 mM sodium arsenate [As(V)]. The protein's half-life of deactivation at 25 °C was 6.1 min, and its inactivation rate constant K(d) was 1.1 × 10(-1) min(-1). The enzyme was active in a broad pH range from 4.0 to 11.0 with optimum activity at pH 10.0. Phosphatase would remove phosphate group from nucleic acid or dephosphorylation of other enzymes as regulation signaling.
authors.affiliation: Institute of Bioscience and Biotechnology and Center for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Keelung 202, Taiwan.
authors.forename: Ya-Hui
authors.initials: YH
authors.lastname: Chan
authors.forename: Chao-Yi
authors.initials: CY
authors.lastname: Lin
authors.forename: Shou-Hsiung
authors.initials: SH
authors.lastname: Pai
authors.forename: Jenq-Kuen
authors.initials: JK
authors.lastname: Huang
authors.forename: Chi-Tsai
authors.initials: CT
authors.lastname: Lin
mesh_terms: D000595:Amino Acid Sequence; D053502:Arsenate Reductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D006863:Hydrogen-Ion Concentration; D027723:Ipomoea batatas / Q000201:enzymology*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D035281:Plant Tubers / Q000201:enzymology; D016415:Sequence Alignment
chemical_list: D053502:Arsenate Reductases; D010744:Phosphoric Monoester Hydrolases